martin richard whose mother and sister were also gravely hurt. 29-year-old restaurant manager crystal campbell was also killed. she was there with her best friend to take a picture of the friend's boyfriend crossing the finish line. at least 17 of the victims are described as critical. many lost limbs, with most wounds to the lower extremities. doctors are finding dozens of nails and ball bearings in some victims. >> there are a variety of sharp objects that we found in their bodies, probably this bomb had multi-multiple metallic fragments in them. >> there are people who have lost their lives or have lost limbs. so, i'm very fortunate and i wish everybody else the best. >> the fbi's evidence response team is processing the scene with help from the atf and other investigators, collecting evidence and combing for clues. overnight, the investigation led to the search of an apartment belonging to a college student described as a saudi national, tackled as he was running from the scene with burns to his body. is he cooperating and has been ruled out as a suspect and a man who says is he a roommate